Latvian is fun when it comes to questions.
There are lots of different question words and it seems like almost all of them start with a K. (They don't all though. There's vai and cik , for example.)
If you think that's weird, look at English - lots of ours start with Wh. Same concept and execution as our " Who? What? When? Where? Why?"
Some of them, notably the ones that correspond to the different forms, expect an answer in a certain form. For example, kas and ko both translate to what/who in English, but with an important difference: kas expects a nominative answer and ko expects an accusative answer.
Nominative generally means the subject of a sentence. Accusative means the direct object of the sentence. A direct object is something that is acted upon by the verb. More on this later.
The most common question words are:
Kas? -- What? Who? -- Asks about the subject
Kā? -- Whose? Of whose?
Kam? -- To whom / what / which? For whom / what / which?
Ko? -- What? Who? -- Asks about the direct object
Ar ko? -- With what? With whom?
Kur? -- Where?
Kāpēc? -- Why?
Kad? -- When?
So, for example, I could ask: " Kur ir pele?" [Where is the mouse?] Because kur is asked for the locative form, I would answer in the locative: " Kaķī." [In the cat.]
Endings give so much information - just one word, kaķī, gives me three in English when translating. Don 't be afraid to speak simply, you're more likely to be correct.
But if you answered: "Kaķis." it would make no sense at all! You would be answering along the lines of "the cat" and forgetting all about the important part of the question: WHERE is the mouse? The Latvian you're speaking to would be waiting patiently for you to get around to finishing your sentence, perhaps with a tale of a daring and adventurous mouse escaping the cat.